(a) Field of the Invention
The invention relates to an array substrate of a thin film transistor liquid crystal display (TFT-LCD) and a method for fabricating the array substrate of the TFT-LCD.
(b) Description of the Related Art
Nowadays, a thin film transistor liquid crystal display (TFT-LCD) that incorporates active-matrix addressing technology has gone mainstream because of its low power consumption, high resolution, and swift response. Moreover, the fabrication of an amorphous silicon thin-film transistor (a-Si TFT), among all kinds of thin-film transistors, becomes dominant in the active-matrix addressing technology.
The configurations of an a-Si TFT are mainly classified as four types including the following: 1. normal coplanar, 2. inverted coplanar, 3. normal staggered, and 4. inverted staggered. Though each type of TFT configurations may have its own design features and suitable application, the inverted staggered configuration is more widely used in a-Si TFT fabrication.
In the fabrication of a TFT LCD, an array substrate is first provided on which a TFT matrix is formed through repetitive semiconductor processes such as film deposition, lithography, and etching to result in specific circuit operations. Then, liquid crystal materials are injected in the gap formed between the array substrate and a color filter substrate arranged parallel to the array substrate, and they together form a TFT LCD panel. Finally, the TFT LCD panel and other devices such as a driver IC, a circuit board, and a backlight are put together in a chassis and assembled into a finished product.
However, during the fabrication of an a-Si TFT LCD, some dust particles suspended in the air of the fabrication environment may fall on the array substrate. In that case, once an amorphous silicon layer is deposited on the array substrate, amorphous silicon materials may enclose the dust particles to form many tiny protrusions referred to as amorphous silicon particles, which are seldom completely removed by subsequent etching processes. Thus, the residual amorphous silicon particles, which are hardly ever detected compared to common particles, may result in a potentially serious defect of an a-Si TFT LCD. Particularly, when the amorphous silicon particles leave residues on the active areas (light-transmitting areas) of the array substrate, a weak capacitance coupling effect may occur between the residues and a pixel electrode to considerably decrease the production yield of an a-Si TFT LCD.